Centrifugal separators have a drive motor which can be provided in various ways in relation to the centrifuge rotor. According to a common variant, the drive motor is located beside the spindle of the centrifuge rotor. The power transmission from the drive motor to the spindle can then be obtained by means of a drive belt, wherein the axis of rotation of the drive motor is parallel to the spindle, or by means of a gear box, wherein the axis of rotation of the drive motor may be perpendicular to the spindle. A disadvantage of these known solutions is energy losses in the power transmission. Furthermore, the components included in the power transmission, especially the drive belt and the gear box, are subjected to wear.
According to another variant, the rotor shaft of the drive motor and the spindle are provided after each other along a common axis. The spindle is then directly connected to the rotor shaft of the drive motor via a coupling, and thus without any power transmission in the form of a drive belt or a gear box. The spindle is supported by two bearings, a first upper spindle bearing and a second lower spindle bearing. The two spindle bearings thus absorb both axial and radial forces. The drive motor is provided below the lower spindle bearing, wherein the rotor shaft of the drive motor is connected to the spindle via a coupling. Such a centrifugal separator is disclosed in DE-A-3714627. A disadvantage of this known solution is that the total height of the centrifugal separator is high.
GB-A-251,593 discloses a similar centrifugal separator, wherein the upper spindle bearing and the lower spindle bearing have been provided in the proximity of each other in a common bearing unit arranged to absorb axial and radial forces.
EP-B-1 392 446 disclosed another similar centrifugal separator where the upper spindle bearing and the lower spindle bearing have been provided in a common bearing unit for absorbing axial and radial forces.
A disadvantage of these two solutions is that the bearing units are complicated. The bearing units shall, except for absorbing axial and radial forces, also permit the spindle to pivot.